A number of overboarding fixtures have evolved since the need for towing acoustic hydrophone arrays through the ocean became known. Several designs constrain the cable to undergo varying amounts of bending over short radii, increasing the tension with which the array is wrapped upon the winch reel, and offering the possibility of fouling, crushing, scoring, abrading, etc., and subsequent damage to the hydrophones.
An early design by J. H. Wilson and disclosed in U.S. Pat. No. 2,660,382 concerns a level winding device for winding a cable on a cable drum. A number of sheaves in a guide head receives a cable for assuring a level winding of the cable. This design is highly suited for winding a relatively heavy steel cable onto a drum and can sense and make allowances for stretched, thinner diametered cables.
The level winder of S. M. Stone et al in U.S. Pat. No. 2,340,436 guides the cable through a guide head to enable the winding of the cable on a drum. Reciprocal motion by the guide head along the drum axis maintains an effective leverage to guard against distortional strain of the cable load. Properly dimensioned sheaves receive and guide the cable during the winding operation and are capable of upward motion so that each succeeding layer can be wound.
Displacement of a carriage carrying a winch drum was relied upon by J. R. Smith et al in U.S. Pat. No. 3,456,899. Winding of a cable on a drum, perpendicular with respect to the drum axis, was even wound by a novel sensing and coupling. A tangle-free winding of a rod-like material about a reel relied on an improved electromechanical sensing device used to control the traverse movements of the carriage in accordance with a desired lag angle and a desired manner and rate of coiling of the rod-like material about the reel.
Although the afore-identified devices of the prior art all represent noteworthy advances in the state-of-the-art, it appears that one persistent, consistent problem remains. The conventional cable spooling techniques, particularly those associated with overboarding operations, have the problem that the armored tow cable tends to abrade and roughen the surfaces of the overboarding fixture, the fairlead structure, which consequently abrades and damages the elongate instrumentation array as it passes over the abraded and roughened surfaces.
Thus, there is a continuing need in the state-of-the-art for an overboarding fairlead having the capability to pass an abrasive towing cable and an elongate instrumentation array that does not damage the array.